1. Field of the Invention
C.C.M. Gutjahr, in his paper "Carbonization Measurements of Pollen-Grains and Spores and Their Application", Doctorate Thesis at the University of Leiden, June, 1966, studied the degree of carbonization of pollen grains and spores in geologic specimens, pointing out that this could be employed to determine organic diagenesis in areas or intervals devoid of coal. The degree of carbonization of palynomorphs is indeed an index of the level of organic metamorphism to which also other organic matter in the sediment has been subjected, including the precursors of petroleum. Among the factors causing carbonization which have been reported are temperature, time pressure and radioactivity, and of these, particular importance is on the time-temperature relationship of the specimens being investigated. Gutjahr estimated the degree of diagenesis in coals using the measurement of absorption of light by the palynomorph exine. Of course, since percentage of absorption is simply the converse of percentage translucency, either measurement could be employed in carbonization studies. Gutjahr also pointed out the desirability of using standard chemical preparation techinques to prepare the specimens for study and cautioned palynologists of the importance of selecting a type for study that will give low-absorption values when slightly carbonized.
While the date in Gutjahr's thesis was limited to the correlation between the carbonization of pollen grains and spores and the diagenesis found in the metamorphism of coals, he speculated that other correlations with sediment properties might be obtained, such as the use of palynomorphs in studying the hydrocarbon potential of geologic areas (i.e., determining whether petroleum-forming conditions had been encountered in the past by source rocks), but he went no further than this. We have found that a particular manipulation in collecting and in using data concerning carbonization of palynomorphs in samples obtained near the surface of the earth can be used for a much more significant purpose: obtaining near-surface data that directly indicate the presence or absence and location of a more deep-seated mineral deposit, including petroleum, coal, etc.
2. Description of the Prior Art
The Gutjahr paper has already been mentioned. One of us (Grayson) in a paper "Relationship of Palynomorph Translucency to Carbon and Hydrocarbons in Clastic Sediments" at the Centre National de la Recherche Scientifique at Paris 15-17 September, 1973, at the International Colloquium of Petrography, presented data using measurement of the amount of light absorbed by or transmitted through various specific palynomorphs as a key to the measure of carbonization. Specific taxa were selected for the study because translucency characteristics vary among different types of pollen and spores. All measurements were made on the same taxon. It was shown that the percent translucency varied from shallow depths in the well (of the order of 2,500 feet) to depths of the order of 14,000 to 16,000 feet and that the measurements tended to correlate with analyses of samples from the well for carbon, oxygen, nitrogen, and hydrogen. No data on light transmission or absorption from specific taxa collected from samples from shallow locations were given in this paper.
Others in the petroleum industry subjectively utilize palynomorph (visual) color as an indicator of source rock diagenetic maturation. However, study of the literature in the field of palynology indicates to us that others have not made use in hydrocarbon and mineral prospecting of light transmission properties from palynomorphs collected in the shallow subsurface region of wells.